avg
功能
用于返回选中字段的平均值。
语法
AVG([DISTINCT] expr)
参数说明
epxr
: 被选取的表达式,可选字段 DISTINCT 参数。
返回值说明
返回值为数值类型。
示例
MySQL > SELECT datetime, AVG(cost_time)
FROM log_statis
group by datetime;
+---------------------+--------------------+
| datetime | avg(`cost_time`) |
+---------------------+--------------------+
| 2019-07-03 21:01:20 | 25.827794561933533 |
+---------------------+--------------------+
MySQL > SELECT datetime, AVG(distinct cost_time)
FROM log_statis
group by datetime;
+---------------------+---------------------------+
| datetime | avg(DISTINCT `cost_time`) |
+---------------------+---------------------------+
| 2019-07-04 02:23:24 | 20.666666666666668 |
+---------------------+---------------------------+